1. Field of Invention
The invention relates to an electric vehicle drive control apparatus, an electric vehicle drive control method, and a program thereof.
2. Description of Related Art
In a conventional electric vehicle drive control apparatus installed in an electric vehicle, so as to generate torque of a drive motor, that is, drive motor torque, and transfer the drive motor torque to driving wheels, the drive motor receives direct current from a battery and is thereby driven at the time of power running (driving) so as to generate drive motor torque. At the time of regeneration (electric power generation), the drive motor receives torque due to inertia of the electric vehicle, and generates DC current, and sends the current to the battery.
Therefore, in the aforementioned electric vehicle drive control apparatus, an inverter is disposed between the drive motor and a drive motor control device. The inverter is driven based on a drive signal from the drive motor control device. At the time of power running, the inverter receives DC current from the battery, and causes the generation of U-phase, V-phase and W-phase currents, and sends the phase currents to the drive motor. At the time of regeneration associated with the braking of the electric vehicle, the inverter receives the phase currents from the drive motor, and causes the generation of DC current, and sends the current to the battery.
However, in the above-described conventional electric vehicle drive control apparatus, if the voltage of the battery, that is, the battery voltage, becomes high, for example, as in a case where the electric vehicle is run on a long downhill, the load on the inverter becomes great. Furthermore, to drive the inverter, the switching of a transistor of the inverter is performed, and therefore, a surge voltage, which is a transient voltage, momentarily occurs. The surge voltage increases with increases in the battery voltage. Therefore, the load on the inverter increases with increases in the battery voltage.